J/A+A/636/A12 1.4≤z≤5.0 QSOs luminosity function (Retana-Montenegro+, 2020)
The optical luminosity function of LOFAR radio-selected quasars at
1.4 ≤ z ≤ 5.0 in the NDWFS-Bootes field.
Retana-Montenegro E., Roettgering H.J.A.
<Astron. Astrophys. 636, A12 (2020)>
=2020A&A...636A..12R 2020A&A...636A..12R (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Redshifts
Keywords: quasars: general - quasars: supermassive black holes -
radio continuum: galaxies - galaxies: high-redshift
Abstract:
We present an estimate of the optical luminosity function (OLF) of
LOFAR radio-selected quasars (RSQs) at 1.4<z<5.0 in the 9.3deg2 NOAO
Deep Wide-field survey (NDWFS) of the Bootes field. The selection was
based on optical and mid-infrared photometry used to train three
different machine learning (ML) algorithms (Random forest, SVM,
Bootstrap aggregation). Objects taken as quasars by the ML algorithms
are required to be detected at ≥5σ significance in deep radio
maps to be classified as candidate quasars. The optical imaging came
from the Sloan Digital Sky Survey and the Pan-STARRS1 3{PI} survey;
mid-infrared photometry was taken from the Spitzer Deep, Wide-Field
Survey; and radio data was obtained from deep LOFAR imaging of the
NDWFS-Bootes field. The requirement of a 5σ LOFAR detection
allowed us to reduce the stellar contamination in our sample by two
orders of magnitude. The sample comprises 130 objects, including both
photometrically selected candidate quasars (47) and spectroscopically
confirmed quasars (83). The spectral energy distributions calculated
using deep photometry available for the NDWFS-Bootes field confirm
the validity of the photometrically selected quasars using the ML
algorithms as robust candidate quasars. The depth of our LOFAR
observations allowed us to detect the radio-emission of quasars that
would be otherwise classified as radio-quiet. Around 65% of the
quasars in the sample are fainter than M1450=-24.0, a regime
where the OLF of quasars selected through their radio emission, has
not been investigated in detail. It has been demonstrated that in
cases where mid-infrared wedge-based AGN selection is not possible due
to a lack of appropriate data, the selection of quasars using ML
algorithms trained with optical and infrared photometry in combination
with LOFAR data provides an excellent approach for obtaining samples
of quasars. The OLF of RSQs can be described by pure luminosity
evolution at z<2.4, and a combined luminosity and density evolution at
z>2.4. The faint-end slope, α, becomes steeper with increasing
redshift. This trend is consistent with previous studies of faint
quasars (M1450≤-22.0). We demonstrate that RSQs show an evolution
that is very similar to that exhibited by faint quasars. By comparing
the spatial density of RSQs with that of the total (radio-detected
plus radio-undetected) faint quasar population at similar redshifts,
we find that RSQs may compose up to ∼20% of the whole faint quasar
population. This fraction, within uncertainties, is constant with
redshift. Finally, we discuss how the compactness of the RSQs
radio-morphologies and their steep spectral indices could provide
valuable insights into how quasar and radio activity are triggered in
these systems.
Description:
The catalog of spectroscopic and photometric presented here are used
to calculate the optical luminosity function of radio-selected quasars
in the NDWFS-Bootes field.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
photom.dat 69 47 Photometric catalog
spectros.dat 69 83 Spectroscopic catalog
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See also:
J/ApJS/161/9 : X-ray survey of the NDWFS Bootes field (Kenter+, 2005)
J/ApJ/641/140 : Optical counterparts in the NDWFS Bootes field (Brand+, 2006)
J/ApJ/772/26 : AGN with WISE. II. The NDWFS Bootes field (Assef+, 2013)
Byte-by-byte Description of file: photom.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Source Source name (JHHMMSS.ss+DDMMSS.s)
21- 29 F9.5 deg RAdeg Right ascension (J2000)
31- 38 F8.5 deg DEdeg Declination (J2000)
40- 43 F4.2 --- zph Photometric redshift
45- 49 F5.2 mag imagPS Pan-Starrs i-band magnitude (AB)
51- 56 F6.2 mag 1450MAG Absolute magnitude at 1450Å
58- 63 F6.2 mJy F150MHz 150MHz LOFAR total flux density
65- 69 F5.2 mJy e_F150MHz rms uncertainty on F150MHz
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Byte-by-byte Description of file: spectros.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Source Source name (JHHMMSS.ss+DDMMSS.s)
21- 29 F9.5 deg RAdeg Right ascension (J2000)
31- 38 F8.5 deg DEdeg Declination (J2000)
40- 43 F4.2 --- zsp Spectroscopic redshift
45- 49 F5.2 mag imagPS Pan-Starrs i-band magnitude (AB)
51- 56 F6.2 mag 1450MAG Absolute magnitude at 1450Å
58- 63 F6.2 mJy F150MHz 150MHz LOFAR total flux density
65- 69 F5.2 mJy e_F150MHz rms uncertainty on F150MHz
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Acknowledgements:
Edwin Retana-Montenegro, edwinretana(at)gmail.com
(End) Patricia Vannier [CDS] 03-Feb-2020